Chapter 14 Flashcards
What is a nerve impulse?
An electrical signal sent along neurones throughout the body.
The Central Nervous System
Consists of the brain and spinal cord, which contain relay neurones.
The Peripheral Nervous System
Consists of all the other nerves in your body, composed of neurones.
Describe the human nervous system in terms of coordination and regulation of body functions.
Stimuli in the environment such as sound, smell, temperature etc. are picked up by receptors which send a nerve impulse to the coordinator connected to the CNS which sends the signal to the effector (organ/s) which forms a response and produces an action.
Sensory Neurone Diagram
look at your notes: receptor cell, myelin sheath, axon, cell body
Relay Neurone Diagram
look at your notes: dendrites pre-synaptic terminal, axon, cell body
Motor Neurone Diagram
look at your notes: dendrites, myelin sheath, axon, cell body, muscle
What are voluntary actions and involuntary actions?
Voluntary actions are actions the brain decisively chooses to do and involuntary actions are actions we do not choose to do, but can control. conscious, and unconscious.
Describe a simple reflex arc
Receptor, sensory neurone, relay neurone, motor neurones and effector
What is simple reflex action?
An automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands). Basically, fast involuntary action.
What is a synapse?
a junction between two neurones
Whats the structure of a synapse?
The structure of a synapse includes, vesicles containing neurotransmitters, synaptic clefts and protein neurotransmitter receptor molecules.
Describe an impulses way through the synaptic gap
When an impulse comes close to the pre-synaptic membrane, the vesicles containing neurotransmitters release the neurotransmitters near the pre-synaptic membrane. Which diffuses across the synaptic cleft and into the post synaptic membrane containing neurotransmitter receptor molecules. The connection transfers it back into an impulse, as neurotransmitters are a chemical version of the impulse, transferring back to an electrical signal. The mitochondria add energy to reform the neurotransmitter.
Reflex Arcs One-Way
In reflex arcs, the impulse travels one-way because it would be quicker. The nerves don’t go from the sensory neurone to the CNS to the brain to the motor neurone, rather sensory neurone to the CNS to the motor neurone.
Drugs effect on the synapses
Drugs influence the transmission of impulses by influencing the release of neurotransmitters or by interacting with receptors either by stimulating them or inhibiting them.
Excitatory drugs
Amphetamines; drugs that increase the activity of the nervous system.
- Amphetamines stimulate the release of neurotransmitters in the brain, increasing brain activity and alertness. Also losing appetite.
Inhibitory drugs
Heroin and Beta blockers; reduces the activity of the nervous system.
- Heroin and Beta blockers reduce the effects of neurotransmitters. Heroin reduces the release of neurotransmitters and therefore, pain. Beta blockers block the receptors for neurotransmitters: this reduces blood pressure and heart rate.
Describe a nerve impulse
an electrical signal that passes along nerve cells called neurones
Describe the human nervous system
The nervous system contains the central nervous system which consists of the brain and spinal cord and the peripheral nervous system which contains all of the other nerves. They are responsible for coordination and regulation of body functions by detecting stimuli.
Identify motor (effector), relay (connector) and sensory neurones from diagrams
sure
sense organs
groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
Identify the structures of the eye
Sure. They contain the cornea, iris, pupil, lens, retina, optic nerve and blind spot.
Describe the function of cornea
The cornea refracts light
Describe the function of iris
It controls how much light/ the intensity of light that enters pupil
Describe the function of lens
Changes its shape to help focus light onto retina
Describe the function of retina
Inner light-sensitive layer which contains rod cells that work in dim light and cone cells that detect colour ad details.
Describe the function of optic nerve
carries nerve impulses from the eye to the brain
Explain the pupil reflex in terms of light intensity, antagonistic action of circular and radial muscles in the iris and pupil diameter
Bright light:
- pupils diameter decreases in size to let in less light to protect retina.
- circular muscles contract
- radial muscles relax
Dim light:
- pupil diameter increases in size to let more light in to see properly.
- circular muscles relax
- radial muscles contract
Explain accommodation to view near and distant objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light
Near:
- contraction of the ciliary muscles to counteract pressure in the eyes.
- suspensory ligaments become more slack
- lens is pulled into a fatter/spherical shape by the suspensory ligaments
- light rays are refracted more
Distant:
- ciliary muscles relax
- pressure inside the eye cause the suspensory ligaments to be tight
- lens is pulled into a thin shape by the suspensory ligaments
- light rays are refracted as they pass the lens and it focused on the retina
State the distribution of rods and cones in the retina of a human
the fovea in the centre of the retina contains cones and no rods, while the rest of the retina contains rods and a few cones.
Outline the function of rods and cones
Both are light sensitive. Rods are sensitive to light of low intensity and send impulses when it is dark; which allows us our night vision and cones are sensitive to light of high-intensity. There are three different kinds of cones that are sensitive to different wavelengths of light. Absorbing light of different colours for colour vision.
Identify the position of the fovea
In the middle of the retina on the same horizontal level as our blind spot.
hormone
a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
Identify specific endocrine glands and their secretions
Adrenal glands produce adrenaline, pancreas produce insulin, testes produce testosterone and ovaries produce oestrogen
Describe adrenaline
the hormone secreted in ‘fight or flight’ situations that causes increased breathing and pulse rate and widened pupils
Give examples of situations in which adrenaline secretion increases
Situations where you may be injured or die, the so called “fight or flight” situations. Like a school shooting.
State the functions of insulin, oestrogen and testosterone
Insulin:
lowers the glucose concentration in the blood
Oestrogen:
Controls the menstrual cycle and stimulates development of secondary sexual features during puberty
Testosterone:
stimulates development of secondary sexual features during puberty
Discuss the role of the hormone adrenaline in the chemical control of metabolic activity
- Causes the increase of the blood glucose concentration to provide enough energy for increased levels of activity, such as running or fighting
- Increases the pulse rate to allow more blood to the muscles for increases levels of activity.
Compare nervous and hormonal control systems in terms of speed and longevity of action
Nervous system:
- fast
- longevity of an action is short lived
control system:
- slow
- longevity of an action is longer lasting
homeostasis
the maintenance of a constant internal environment; it is the control of internal conditions within set limits
Explain the concept of control by negative feedback
Negative feedback is when the opposite is done to keep something constant. For example, if our body temperature increases, then negative feedback would respond to make us cool down and come close to our normal temperature.
Describe the control of the glucose concentration of the blood by the liver and the roles of insulin and glucagon from the pancreas
When there is an increase in the glucose concentration in the blood, the pancreas detects this and releases insulin into the blood which stimulates the liver cells to convert the glucose into glycogen. The liver absorbs a lot of the glucose in the blood so the glucose concentration comes back to normal.
When your glucose concentration decreases in the blood, the pancreas then releases the hormone glucagon into the blood which stimulates the liver cells to break down glycogen to glucose. Increasing the glucose concentration in the blood to normal.
Outline the symptoms and treatment of
type 1 diabetes
Type 1 diabetes is caused by an autoimmune response in which antibodies attack cells in the pancreas which usually make insulin. This means that no insulin can be produced. It is usually treated by patients injecting insulin in themselves.
Name and identify on a diagram of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue
ok
Describe the maintenance of a constant internal body temperature in humans in terms of insulation, sweating, shivering and the role of the brain
Your brain detects a loss of heat and gain of heat in the blood and can do the following responses.
- we can conserve heat with the fat beneath our skin when it is too cold as it is a good insulator.
- Mammals have fur or hair which traps a layer of air close to the skin. Air is a poor conductor of heat so it reduces the loss of heat to the atmosphere by keeping convection currents of air away. Therefore, hair erector muscles contract to make you hair stand up to make a layer of air.
- sweating helps to cool down the body as the sweat carries away heat when it evaporates off the skins surface.
- the body shivers as the body muscles contract spontaneously to release heat from respiration.
Describe the maintenance of a constant internal body temperature in humans in terms of vasodilation and vasoconstriction of arterioles supplying skin surface capillaries
- to lose heat, the arterioles widen as the muscles around it relax (vasodilation) and there is an increase in blood flow through the capillaries so more heat is lost to the environment.
- to gain heat, the arterioles constrict as the muscles around it contract (vasoconstriction) and there is an decrease in blood flow through the capillaries and the blood is diverted beneath the fat layer so less heat is lost to the environment.
gravitropism
a response in which parts of a plant grow towards or away from gravity
phototropism
a response in which parts of a plant grow towards or away from the direction from which light is coming
Investigate gravitropism and phototropism in shoots and roots
Explain phototropism and gravitropism of a shoot
they are examples of the chemical control of plant growth in terms of auxins
Explain the role of auxin in controlling shoot growth
auxin is made in shoot tip (only), the auxin spreads through the plant from the shoot tip and is unequally distributed in response to light and gravity. The plant then changes position as auxin stimulates cell elongation
Describe the use in weedkillers of the synthetic plant hormone 2,4-D
Synthetic auxins are selective weedkillers. While most cereal crops are narrow leaved, weeds are broad leaved. So herbicides like 2,4 -D that are sprayed on the crop run off the leaves of the crops into the weeds. The auxins increase growth in the leaves, however the weeds can not provide enough energy to maintain this rate of growth so eventually they die.
